Stepper motor driven aperture/shutter systems have been notorious for the shutter blades oscillating, under damped behavior, when opened to a desired aperture position. Much has been done to damp this oscillating motion, such as the use of elaborate controls for driving the stepper motor. However, the use of elaborate motor controls is expensive and complicates the operation of the aperture/shutter system.
Another method of addressing the oscillating motion of shutter blades is disclosed in U.S. Pat. No. 3,852,786, issued in the names of Onda et al. on Dec. 3, 1974. The Onda patent discloses a shutter assembly having a plurality of shutter blades divided in a shutter-opening blade group and a shutter-closing blade group. A shutter actuating mechanism independently actuates both groups of shutter blades to effect opening and closing of a shutter aperture. A flexible spring plate having a series of protuberances thereon is disposed along the path of travel of the shutter blades. As each blade group nears the end of its working stroke, the shutter blades collide with selected ones of the protuberances to effect flexing of the spring plate to cause movement of other ones of the protuberances into firm frictional engagement with the shutter blades. Consequently, the shutter blades are pressed together to absorb the kinetic energy of the shutter blades and effectively dampen their rapid movement.